Hundreds of volunteers have been asked to stay away from a search for an "outstanding cricketer" who went missing from Royal Welsh Show.
James Corfield, 19, has not been seen since he left the White Horse pub in Builth Wells, Powys, in the early hours of Tuesday morning.
He had been due to meet family at the showground where he was camping with friends but never arrived.
Police said for safety reasons, only trained officers should search.
His mother Louise Corfield said they were "desperate to know where he is".
Following the closure of the festival, officers are searching the Royal Welsh showground and the young people's village.
The Mid and West Wales Fire and Rescue Service's drone is being used to spot for signs along the River Wye.
On Thursday about 200 volunteers joined mountain rescue teams, police and dog units, officials from young farmers' clubs and the fire service in the search for Mr Corfield.
Sup Int Jon Cummins said members of the public should stay away for their own safety on the third day of the search for the 19-year-old.
He said: "While we fully understand the concern from the community and the desire to assist in the search for James, it is vitally important at this stage that we have only specially trained officers and our partners out there looking for him.
"Staying away is the best possible assistance the public can give us today and of course reporting any new information they may have to us by calling 101 immediately."
Montgomery Cricket Club cancelled its match on Saturday after players, supporters and friends helped with the search for Mr Corfield earlier in the week.
In a statement the club said: "He's an outstanding cricketer and friend to everyone at the club, and we can't wait to get him back."
Mountain rescue teams with kayaks and boats resumed their search of the River Wye at 08:00 BST on Thursday but were stood down at about 20:30.
Mark Jones, of Brecon Mountain Rescue Service, said gardens, sheds and grass verges had been searched.
He said police were continuing to study CCTV footage to understand where Mr Corfield, a member of Shropshire-based Chirbury & Marton Young Farmers Club, went after he left the White Horse pub.
Mr Corfield is 6ft 2in tall, of slim build, with short brown hair and was last seen wearing a blue Abercrombie and Fitch shirt and jeans.